“Gone Girl” is a movie that gnaws at you. At its surface, it’s a tightly sculpted thriller that burrows into the gruesome particulars of marriage at its most monstrous. Yet beneath the dismembered coupling of picture-pretty Nick and Amy Dunne, David Fincher and Gillian Flynn find the ugly truths rotting at the core of the American marriage complex.

We are told in life that the ideal romantic partner is someone who “brings out the best in you” or makes you “want to be your most you.” But then that flimsy illusion fades, and the miserably hitched must resign themselves to a lifetime of biting their tongues at dinner parties while privately dreaming of ruination. “That’s marriage!” as Amazing Amy (Rosamund Pike) says after she and Nick (Ben Affleck) have ruinously turned against each other. [BEWARE SPOILERS BELOW!]

“I was most interested in the idea of narcissism as a way to hold two people together,” David Fincher said Thursday night at a Los Angeles Q&A with Film Independent’s Elvis Mitchell. “And the notion that we project the best version of ourselves not only to seduce somebody that we imagine to be perfect for us but also perfect for our narcissistic rejection. Then three years down the line the other person in the contract says, ‘I can’t get it up for this anymore. I can’t be your soulmate. I was never that person and I am done.’ And I love the wrath that inspired.”

“It’s that thing where you look over at your wife or girlfriend and you see them holding their tongue and then five years later they unleash all of their retribution. I thought that was funny,” Fincher also said following the rapturously applauded Film Independent screening. The raucous audience was, clearly, in on the jokiness of the film. “The movie is funny. It’s funny because it’s horrifying.”

Fincher does not care about pedantic interpretations of his films. And he’s combative. Mitchell would make observations and Fincher would just click his tongue and go “huh” or “okay” or “no.”

As anyone who has seen a Fincher film knows, he’s a principled misanthrope. “I don’t think any place is safe if you bring human nature into it,” he told the full house of moviegoers. He doesn’t enjoy watching his films with a public audience. “Nothing will convince you more that your movie is way too fucking long than opening the New York Film Festival…It’s like getting a Cesarian in front of 700 people,” he said.

At the New York premiere (covered by Anne Thompson here), Fincher felt that “Gone Girl,” at two-and-a-half hours, was too long: “You see it in a room with a bunch of callous sophisticates and you just go, ‘God these [characters] just yak on and on. Will somebody shut these fucking people up?” (Read about how the film was edited in our interview here.)

Even so, it’s a movie that sets people talking, and it follows you home at night. There’s an ongoing misogyny debate, which is the nature of the beast when you’ve got an angry female protagonist who’s both a victim of suburban entrapment and psychotic. “Gone Girl” is constantly shifting alliances. But it doesn’t tell you how to feel so much as show you how it is feeling.

“The movie is completely hyperbolic. It never occurred to me that you could have a movie that was a mystery and that could hand the baton off to this absurdist thriller and then that could hand off the baton and become this satire,” Fincher said.

So who’s side is the director on, anyway? “I root for Rosamund. There are parts of the movie where I go, oh yeah, ‘Go Amy.’ I love Amy. I love seeing her planning out when she’s going to take her own life. I think that’s hilarious.”

Below are more highlights from the interview, which dove deep into Fincher’s directorial anxieties, why he can’t re-watch his older movies and what drove him into moviemaking. As a child watching movies he thought, “This is an insane way to make a living. Where do I go to surrender?”How does Fincher engineer dread?

“It’s not so much dread. It’s that everything is balanced. I want to see arguments between characters where I agree with them, and situations that, depending on the outcome, it’s going to be horrible for one of the participants. I’m interested when you have a hard time rooting for one side as opposed to the other because it’s going to come at a cost.”

Are we over-thinking “Gone Girl”?“The game Ben gives her, Mastermind, [has] absolutely no importance. There is no significance at all. I think it was the only one we could legally clear. And of course everyone goes up to me and says, “Oh yeah, Mastermind.” Red herrings are fun but they are also irritating and distracting.”

Why Ben Affleck?“He fits hand-in-glove with what Nick has to be. He has to be the homecoming king. In a movie where you have a pivotal scene where a person stands next to a poster of his missing wife and is smiling, that’s something he knows how to do. I could go through Google. I could just show him one: ‘I want one of these.” He gets his feet run over with a steamroller. And then he gets his ankles run over. Then he gets his shins run over, then his knees and then both femurs, his pelvis, and his lower back. You just get crushed. Ben has been through that. He knows what it means to be tossed by the 35 foot waves of public perception. He also has great wit about it. He knows it has nothing to do with you. At a certain point it has nothing to do with you at all. The symbol of you becomes more important than your actual participation.”

Why draws Fincher to such dark material?“There are plenty of movies where people turn out okay and justice is served. The curse of working in cinema is that nothing is treated as accidental and offhanded. We’ve been fed this idea for a hundred years that the reason movies cost so much is because it’s all been tested. Everything has been worked out for your enjoyment. Why would a movie cost $150 million dollars? ‘Because we had to make sure it was just so’… I also like movies where the audience [recoils]. That’s as valid as cheering for the exploding Death Star.”

Have studios ever tried to change one of his endings?“They wanted the ending of ‘Seven’ to be ‘Fatal Attraction.’ They wanted it to be Brad in a car, driving on sidewalks to get across town because Gwyneth was drawing a hot bath and Kevin Spacey was breaking into their apartment. That’s valid if you’re a movie studio. You want something tangible that you can point to. But instead she dies. It’s better. She’s been dead for 14 hours. She dies offscreen horribly.”